method 1: Take two points to establish a straight line, Calculator the straight line analytic formula. Plug in the third point coordinates to see if the straight line and Equation is satisfied.

method 2: Let the three points be A, B, C. Use vector to prove: λAB=AC (where λ is non-zero real number).

method 3: Use the point difference method to find AB slope and AC slope, equal to the Three point collinear.

method 4: Using the Menelaus Theorem.

method 5: Use the axiom in geometry that "Two non-coincidence planes have one common point, then they have and only one common straight line through that point." Three point collinear.

method 6: Apply the common (definite) principle "There is and only one straight line at a point beyond the straight line and the known straight line is parallel (vertical)". It's actually the same method.

method 7: Prove that the Angle is 180°.

method 8: Let A, B, C, prove that △ABC area is 0.